1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the zoom lens that are suitably used in electronic cameras, such as a video camera and a digital still camera, a film camera, and a broadcasting camera.
2. Description of the Related Art
A zoom lens for use in an image pickup apparatus, such as a digital camera or a video camera, including a solid-state image pickup element is required to have a compact optical system, a high zoom ratio, and an image stabilizing function.
A positive lead zoom lens in which a lens unit closest to the object side has a positive refractive power can easily achieve a high zoom ratio, and therefore, is frequently used particularly as a zoom lens having a zoom ratio of 10 or more.
As a positive lead zoom lens, a compact five-unit zoom lens having a high zoom ratio is known in which five lens units having positive, negative, positive, negative, and positive refractive powers are arranged in that order from the object side to the image side.
U.S. Pat. Nos. 5,388,004, 5,659,426, 5,771,123, and Japanese Patent Laid-Open No. 2002-228931 disclose five-unit compact zoom lenses in which a fourth lens unit having a negative refractive power is formed by one component.
Further, zoom lenses having an image stabilizing function are also known. In the zoom lenses, image blurring caused when vibration is accidentally transmitted to an imaging system is compensated by moving some of the lens units perpendicularly to the optical axis.
A five-unit zoom lens disclosed in Japanese Patent Laid-Open No. 2000-298235 has an image stabilizing function for correcting image blurring by moving a third lens unit perpendicularly to the optical axis.
Particularly when the image-stabilizing lens unit is moved perpendicularly to the optical axis in the zoom lens, it is required to have a small size and a light weight for the purpose of size reduction and power saving of a moving mechanism.
Moreover, the zoom lens is required to have high optical performance while suppressing changes in aberration during image stabilization. In order to satisfy the above requirements, it is important to properly set the zoom type and the lens configuration of the image-stabilizing lens unit.